1. Field of the Invention
The present invention is related to information handling systems, and, more specifically, to independent control of output current balance between paralleled power supply units of the information handling system.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users are information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes, thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems, e.g., computer, personal computer workstation, portable computer, computer server, print server, network router, network hub, network switch, storage area network disk array, RAID disk system and telecommunications switch.
An information handling system is powered from a power supply system that receives and converts alternating current (AC) power to direct current (DC) power at utilization voltages required by the electronic modules comprising the information handling system. The power supply system tightly regulates these utilization voltages and incorporates over current protection for each of the voltages. To further provide increased reliability of the power supply system, a plurality of power supply units (PSU) may be provided and coupled in parallel so that the loss or malfunction of one or more of the PSUs will not totally disable operation of the information handling system. When PSU output voltages are coupled in parallel some form of load sharing or current output equalization is commonly used to minimize the stresses on all of the power components. A general article addressing the various ways of load sharing between PSUs is discussed in an article from Texas Instruments entitled “Paralleling Power—Choosing and Applying the Best Technique for Load Sharing,” by Laszlo Balogh. This article may be found at the Texas Instruments web site URL: http://focus.ti.com/lit/ml/slup207/slup207.pdf, and is hereby incorporated by reference for all purposes.
Parallel connected PSU current sharing techniques also have a penalty in terms of efficient performance. When all the paralleled PSUs deliver the same amount of current but all are not physically located at the same distance from the load, the PSUs located farthest from the current load will have additional unnecessary distribution power losses. In addition, power supply system load sharing has additional concerns in that not all of the PSUs comprising the power supply system may have equal power output ratings, nor may all of the parallel connected PSUs be functioning at maximum performance or capabilities. There are instances (system fan failure, etc.) where regular techniques of load sharing fail to optimize the reliability of the system because even though the output current is balanced from each parallel connected PSU, the stress levels are not (temperature, airflow, etc.).
For example, one or more of the PSUs may be operating at a higher temperature than the other PSUs, and/or one or more of the PSUs may be operating in a degraded mode of operation, e.g., a cooling fan has malfunctions, an air filter excessively restricts cooling air flow, etc. These factors require that not all of the PSUs can or should deliver the same amount of current to the information handling system load. Commonly owned U.S. Pat. No. 6,664,657 by Jeffrey C. Hailey, discloses a very sophisticated and complex method and system of load sharing between a plurality of PSUs having different operational stress factors. These stress factors may be differences in PSU temperatures, different PSU current output ratings, malfunctions of PSU components, etc. Using the stress factors, current outputs from the different PSUs may be optimized for best reliability of the power supply system. U.S. Pat. No. 6,664,657 is hereby incorporated by reference herein for all purposes. However, a simple and inexpensive way of independently controlling each PSU output current when coupled in parallel has not been available.
Therefore, what is needed a very simple and cost effective way to control load current balance between paralleled PSUs with an analog signal input, allowing additional performance in terms of efficiency and reliability of each PSU coupled in parallel and the ability to balance or unbalance each of the output currents depending upon stress factors of each PSU, and/or distant of each PSU from the information handling system load.